Estimation of Aquifer Connectivity Metrics from Pumping Tests Data

Subsurface flow parameters, such as transmissivity or storativity, are intrinsically heterogeneous and characterized by complex patterns of spatial variability. In the case of transmissivity, the presence of spatially connected flow channels can have significant impact on groundwater flow and contaminant transport. In this study, we investigate numerically the impact of point-to-point flow connectivity on radially convergent flow in constant rate pumping tests, focusing on how connected features influence the estimation of hydraulic parameters. Multiple heterogeneous aquifer systems with different levels of connectivity are synthetically generated and then used to simulate pumping tests. Different pumping test interpretation methods are used to estimate the flow parameters from the time-drawdown data and to investigate how the estimated parameters relate to the underlying heterogeneous distribution of aquifer parameters. In particular, the relations between the estimated parameters and static measures of connectivity, that are independent of the flow pattern, are examined. Results indicate that the estimated transmissivity value approaches the geometric mean of the transmissivity field irrespective of the level of aquifer connectivity. On the other hand, the estimated storativity is seen to be strongly influenced by aquifer point-to-point flow connectivity; yet, this influence is obscured as estimated storativity is also dependent on the spatial distribution of the transmissivity and the relative locations of the observation and pumping wells. The implications of these findings on the interpretation of constant rate pumping tests are discussed.